U.S. 2012/0306403 A1 discloses a driver circuit for powering a direct-current lamp in a non-direct-current lamp fitting. This driver circuit comprises two filament circuits each one consisting of two serial resistors or of two serial coils. U.S. 2014035463A1 and U.S. 2014225520A1 disclose a filament circuit with two parallel RC circuits connected in series between the two input pins and the interconnection of the two RC circuits is the output of the filament circuit. U.S. 2014225520A1 and DE202013000880U1 disclose a filament circuit with one parallel RC circuit connected between the two input pins and the input pin is directly the output of the filament circuit.